Light modulator for MEMS display

ABSTRACT

Electromechanical light modulators and backlight providing efficient, low cost and high performance displays.

RELATED U.S. PATENT DOCUMENTS

U.S. application Ser. No. 12/584,465 filed Sep. 3, 2009 now U.S. Pat.No. 7,995,261 B2 which is included here as reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present inventions relate generally to displays. More particularly,the invention concerns displays comprising electromechanical pictureelements.

Discussion of the Prior Art

Currently liquid crystal displays dominate the flat panel displaymarket. Displays based on electromechanical light modulators have beenproposed as a viable alternate to LCDs. The present inventions discloseelectromechanical light modulators and displays that can compete withLCDs in picture performance, light efficiency and cost.

SUMMARY OF THE INVENTION

The following is a summary description of illustrative embodiments ofthe invention. It is provided as a preface to assist those skilled inthe art to more rapidly understand the detailed design discussions whichfollow and is not intended in any way to limit the scope of the claimswhich are appended hereto in order to particularly point out theinvention.

The specification discloses several electromechanical light modulators.According to illustrative embodiments of the invention, modulatorsinclude one or two electrostatic actuators, a light shutter supportedover a surface of a substrate with a plurality of supports that areattached to the shutter at a first and a second end of the shutter. Inoperation the actuator applies a force to the shutter. The shuttersupports limit the shutter movement in the direction of the force andallow the shutter to move substantially in a lateral direction withrespect to the force. The shutter moves in the lateral direction betweena first and a second position without physical contact with a stationarypart or surface. Each electrostatic actuator includes two electrodesthat are positioned substantially parallel and close distance from eachother. In some embodiments the shutter is conductive and acts as one ofthe actuator electrodes. In other designs the shutter includes a flangeextending from an edge of the shutter at a right angle and forms anelectrostatic actuator with a fixed electrode. The fixed electrode maybe positioned substantially close to the flange to form an efficientelectrostatic actuator.

The shutter supports are located between the shutter and the surfacetherefore in a display shutters may be positioned substantially close toeach other only allowing a space between them for shutter movements. Insome modulators the shutter is supported on the surface with cantileverbeams. The invention discloses a method of manufacturing cantileverbeams and a shutter supported by the cantilever beams. The inventionalso discloses a display comprising: a light absorbing layer havinglight transmitting regions, a backlight including a rear reflector forreflecting light towards the light absorbing layer and a plurality ofmodulators each including a shutter positioned between the backlight andthe light absorbing layer, said shutter having light transmittingregions and a light reflecting surface facing the backlight forrecycling the light emitted from the backlight, wherein light from thebacklight impinging said light transmitting regions of the shuttertransmit through the light transmitting regions of the light absorbinglayer when the shutter is at a first position and are absorbed in thelight absorbing layer when the shutter is at a second position.

The invention also discloses another display comprising: a plurality ofmodulators each including a shutter having light transmitting regions,and a substrate having a surface and a plurality of embedded lightreflectors, wherein said embedded light reflectors cause light to exitthe substrate from said surface of the substrate and converge atrespective light transmitting regions of the shutter.

The foregoing as well as other objects of the invention are illustratedin the accompanying drawings and described in the specification thatfollows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of a shutter assembly according to anillustrative embodiment of the invention.

FIG. 1B is a front view of the shutter assembly shown in FIG. 1A.

FIG. 2A is a top view of an exemplary mold for fabrication of theshutter assembly shown in FIG. 1A.

FIG. 2B is a sectional view taken along line 2B in FIG. 2A.

FIG. 3A is a perspective view of a light modulator according to anillustrative embodiment of the invention.

FIG. 3B is a front view of the light modulator shown in FIG. 3A.

FIG. 3C is a front view of the light modulator shown in FIG. 3Aillustrating a shutter located at a first position.

FIG. 3D is a front view of the light modulator shown in FIG. 3Aillustrating the shutter located at a second position.

FIG. 4A is a perspective view of a light modulator according to anillustrative embodiment of the invention.

FIG. 4B is a front view of the light modulator shown in FIG. 4A.

FIG. 5A is a perspective view of a light modulator according to anillustrative embodiment of the invention.

FIG. 5B is a front view of the light modulator shown in FIG. 5A.

FIG. 6A is a perspective view of a light modulator according to anillustrative embodiment of the invention.

FIG. 6B is a side view of the light modulator shown in FIG. 6A.

FIG. 6C is a perspective view showing shutter supports in the lightmodulator shown in FIG. 6A.

FIG. 6D is a top view of the light modulator shown in FIG. 6A.

FIG. 6E is a top view of the light modulator shown in FIG. 6Aillustrating the shutter located at a first position.

FIG. 6F is a top view of the light modulator shown in FIG. 6Aillustrating the shutter located at a second position.

FIG. 7A is a top view of a light modulator according to an illustrativeembodiment of the invention.

FIG. 7B is a side view of the light modulator shown in FIG. 7A.

FIG. 7C is a top view showing shutter supports in the light modulatorshown in FIG. 7A.

FIG. 7D is a top view of the light modulator shown in FIG. 7Aillustrating the shutter located at a first position.

FIG. 8A is a perspective view of a shutter support according to anillustrative embodiment of the invention.

FIG. 8B is a perspective view of a mold for manufacturing the shuttersupport shown in FIG. 8A.

FIG. 8C is a sectional view taken along line C-C in FIG. 8B illustratinga step for manufacturing the shutter support shown in FIG. 8A.

FIG. 8D is a top view illustrating a step for manufacturing the shuttersupport shown in FIG. 8A.

FIG. 8E is a front view illustrating a step for manufacturing theshutter support shown in FIG. 8A.

FIG. 8F is a front view illustrating a step for manufacturing theshutter support shown in FIG. 8A.

FIG. 8G is a top view illustrating a step for manufacturing the shuttersupport shown in FIG. 8A.

FIG. 8J is a side view illustrating a step for manufacturing the shuttersupport shown in FIG. 8A.

FIG. 9A is a perspective view of a shutter according to an illustrativeembodiment of the invention.

FIG. 9B is a perspective view of a mold for manufacturing the shuttershown in FIG. 9A.

FIG. 9C is a sectional view taken along line C-C in FIG. 9B illustratinga step for manufacturing the shutter shown in FIG. 9A.

FIG. 9D is a perspective view illustrating a step for manufacturing theshutter shown in FIG. 9A.

FIG. 9E is a sectional view taken along line E-E in FIG. 9D illustratinga step for manufacturing the shutter shown in FIG. 9A.

FIG. 9F is a sectional view taken along line F-F in FIG. 9D illustratinga step for manufacturing the shutter shown in FIG. 9A.

FIG. 10A is a perspective view of a display backlight according to anillustrative embodiment of the invention.

FIG. 10B is a side view of the display backlight shown in FIG. 10A.

FIG. 10C is an enlarged view of the area designated 10C in FIG. 10B.

FIGS. 11A to 11D are sectional views illustrating steps formanufacturing an optical layer with embedded light reflectors accordingto an illustrative embodiment of the invention.

FIGS. 12A to 12C are sectional views illustrating steps formanufacturing a substrate with embedded light reflectors according to anillustrative embodiment of the invention.

FIG. 13A is a plan view of a display cover assembly according to anillustrative embodiment of the invention.

FIG. 13B is a sectional view taken along lines 13B in FIG. 13A.

FIG. 14A is a sectional view of a display according to an illustrativeembodiment of the invention illustrating a shutter located at a firstposition.

FIG. 14B is a sectional view of the display shown in FIG. 14Aillustrating the shutter located at a second position.

FIG. 15A is a sectional view of a display according to an illustrativeembodiment of the invention illustrating a shutter located at a firstposition.

FIG. 15B is a sectional view of the display shown in FIG. 15Aillustrating the shutter located at a second position.

DESCRIPTION OF THE INVENTION

FIG. 1A is a perspective view and FIG. 1B is a front view of a shutterassembly 100 according to an illustrative embodiment of the invention.The shutter assembly 100 includes a light shutter 101 that is supportedover a surface 103 of a transparent substrate 102 with supports 104 and105. The supports 104 are attached at a first end 106 of the shutter 101and the supports 105 are attached at a second end 107 of the shutter101. The supports 104 and 105 are substantially straight and areinclined with respect to each other and with respect to the surface 103and form an angle 113 with the surface 103 between 70 and 85 degrees.The supports 104 and 105 are attached to the surface 103 of substrate102 with pads 109 at a distance 114 that is greater than a distance 115between the attachment points of the supports 104 and 105 on the shutter101. The shutter assembly 100 may be constructed to have supports 104and 105 inclined with respect to each other and attached to the surface103 at a distance 114 that is smaller than the distance 115. Thesupports 104 and 105 and the pads 109 are constructed from a thinconductive material and provide an electrical connection from thesurface 103 to the shutter 101. The shutter 101 also is constructed froma thin conductive material or a multilayer film that includes aconductive layer. The shutter 101 includes light transmitting regions108 and light obstructing or blocking regions 110. The light blockingregions 110 are larger (wider and longer) than the light transmittingregions 108. The light transmitting regions 108 transmit 90% or morelight impinging the light transmitting regions 108 and the lightblocking regions 110 blocks at least 99% of the light.

The outer edges or all edges of the shutter 101 are beveled to preventshutter 101 from bending. The shutter assembly 100 may be fabricated ona mold from a metal such as aluminum and silicon alloy. In oneimplementation all surfaces of the shutter 101 may have a lightabsorbing finish. In another implementation the shutter 101 may have alight reflecting first surface 120 and light absorbing second surface121. The light reflecting surface 120 reflects 80% or more light and thelight absorbing surface 121 absorbs 80% or more light.

Depositing a layer of aluminum on smooth surfaces of a mold will provideshutter 101 with a mirror like first surface 120 and a black oxide layermay be formed on the second surface 121 by anodizing. The black oxidelayer may be formed after etching the light transmitting regions 108 sothe inner edges of the light transmitting regions 108 will be coveredwith the black oxide layer.

Also chromium or niobium oxide may be deposited or a black organic resinmay be applied to the shutter 101 surface to form the light absorbingsurface.

Without limitation, the parts of the shutter assembly 100 may have thefollowing dimensions. The shutter 101 may have a width 115 between 50 to1000 micrometer and a thickness from 0.5 to 5 micrometer. The lighttransmitting regions 108 may have a width 122 from 2 to 50 micrometer.The supports 104 and 105 may have a width from 2 to 20 micrometer andthickness from 0.5 to 5 micrometer. The supports 104 and 105 may have alength 112 which is 1.5 to 3 times greater than the width 122 of thelight transmitting regions 108.

FIGS. 2A and 2B illustrate a mold 200 for fabrication of shutterassembly 100. FIG. 2A is a top view of the mold 200 and FIG. 2B is across-sectional view taken along lines 2B in FIG. 2A.

The mold 200 is constructed on the surface 103 of the substrate 102using gray-scale or multiple masks photolithography. A layer ofsacrificial material 201 is deposited on the surface 103. Grooves 203and recessed regions 206 are formed on a surface 205 of the layer 201.The shutter assembly 100 is constructed by depositing and selectivelyetching a thin layer of conductive film on surfaces of the mold 200. Thesupports 104 and 105 are formed on side walls 204 of grooves 203. Theside walls 204 have the same inclination angle 113 as the supports 104and 105 with respect to the surface 103. The recessed regions 206 areprovided to construct the shutter 101 with beveled edges. The bevelededges help to prevent the shutter 101 from bowing or bending. Acombination of directional and conformal deposition of conductivematerial may be used to control relative thickness of supports 104 and105 and the shutter 101.

FIGS. 3A to 3D illustrate a light modulator 300 according to anillustrative embodiment of the invention.

Referring to FIGS. 3A and 3B, the modulator 300 includes the shutterassembly 100 of FIG. 1A and a cover assembly 303. The cover assembly 303includes a transparent substrate 304 supported over the surface 103 ofthe substrate 102 with spacers 306 and 307. Two electrodes 308 and 309are formed on an inner surface 305 of the substrate 304.

The electrode 308 and the conductive shutter 101 form a firstelectrostatic actuator 311 and the electrode 309 and the conductiveshutter 101 form a second electrostatic actuator 312. In operation avoltage potential applied between the electrode 308 and the shutter 101generates an electrostatic force (FIG. 3C) that pulls the supports 104attached at the first end 106 of the shutter 101 to a near uprightposition with respect to the surface 103 and moves the shutter 101laterally (FIG. 3C) to a first position or a voltage potential appliedbetween the electrode 309 and the shutter 101 generates an electrostaticforce (FIG. 3D) that pulls the supports 105 attached at the second end107 of the shutter 101 to a near upright position with respect to thesurface 103 and moves the shutter 101 laterally (FIG. 3D) to a secondposition.

Stored mechanical forces in the supports 104 and 105 return the shutter101 from the first or the second positions to a mechanical rest orneutral position as shown in the FIG. 3B.

In the modulator 300, the first actuator 311 and the second actuator 312each apply a force to the shutter 101 substantially in the samedirection and move the shutter 101 laterally in opposite directions.

In FIG. 3C the arrow 314 indicates the direction of the force applied tothe shutter 101 by the first actuator 311 and the arrow 315 indicatesthe direction of lateral movement of the shutter 101 from the mechanicalrest position to the first position. The shutter 101 moves laterallyfrom the mechanical rest position to the first position at least fivetimes more than in the direction of the force applied by the firstactuator 311 to the shutter 101.

In FIG. 3D the arrow 316 indicates the direction of the force applied tothe shutter 101 by the second actuator 312 and the arrow 317 indicatesthe direction of lateral movement of the shutter 101 to the secondposition.

Applying an increasing voltage to the actuator 311 and a decreasingvoltage to the actuator 312 will gradually move the shutter between thefirst and second positions or applying a fixed voltage to the actuator311 and a variable voltage to the actuator 312 also will move theshutter between the first and second positions gradually.

In a display the electrodes 308 and 309 may be formed wider and sharedby shutter assemblies positioned in successive rows or columns.

FIGS. 4A and 4B illustrate a light modulator 400 according to anillustrative embodiment of the invention. The modulator 400 includes ashutter assembly 401 and a cover assembly 418. The shutter assembly 401includes a shutter 410 that is supported over a surface 403 of atransparent substrate 402 with supports 406 and 407. The supports 407are attached at a first end 408 of the shutter 410 and the supports 406are attached at a second end 409 of the shutter 410. The shutter 410 isformed from an electrical insulator or a dielectric material andincludes light transmitting regions 411 and light blocking regions 412.The shutter 410 further includes a first electrode 405 and a secondelectrode 404. Supports 407 provide an electrical connection from thesurface 403 to the electrode 405 and supports 406 provide an electricalconnection from the surface 403 to the electrode 404.

The cover assembly 418 includes a transparent substrate 413 supported onthe surface 403 with spacers 416 and 417. The cover assembly 418 furtherincludes a transparent conductive layer 415 formed on an inner surface414 of the substrate 413 from a material such as indium thin oxide.

In the modulator 400 the first electrode 405 with the conductive layer415 form a first electrostatic actuator 418 and the second electrode 404with the conductive layer 415 form a second electrostatic actuator 419.

In operation the first actuator pulls the supports 407 to a near uprightposition with respect to the surface 403 and moves the shutter 410laterally to a first position and the second actuator pulls the supports406 to a near upright position with respect to the surface 403 and movesthe shutter 410 laterally to a second position. Stored mechanical forcesin the supports 406 and 407 return the shutter 410 from the first or thesecond positions to a mechanical rest or neutral position as shown inthe FIG. 4B.

FIGS. 5A and 5B illustrate a light modulator 500 according to anillustrative embodiment of the invention. The modulator 500 includesspacers 508 and 509 that are formed on a surface 502 of substrate 501from a polymer and a shutter assembly 503. The shutter assembly 503includes a shutter 507 and shutter supports 505 and 506 that are formedfrom a conductive material and are attached to the spacers 508 and 509with conductive pads 512 and 513.

The modulator 500 further includes two electrodes 510 and 511 that areformed on the surface 502 of the substrate 501. The electrode 510 andthe conductive shutter 507 form a first electrostatic actuator 514 andthe electrode 511 and the conductive shutter 507 form a secondelectrostatic actuator 515.

The shutter assembly 503 may be constructed similar to the shutterassembly 401 and the two electrodes 510 and 511 can be replaced with atransparent conductive layer.

FIGS. 6A to 6F illustrate a light modulator 600 according to anillustrative embodiment of the invention. Referring to FIGS. 6A to 6C,the modulator 600 includes a light shutter 601 constructed from aconductive material and includes light transmitting regions 602 andlight blocking regions 603.

The shutter 601 is supported on a surface 605 of a substrate 604 withfour cantilever beams 606 and 607 that are formed between the shutter601 and the surface 605 and substantially within the boundaries of theshutter 601 (FIG. 6C). A first end of each cantilever beams 606 and 607is attached to the surface 605 with posts 609 and conductive pads 610,and a second end is attached to the shutter 601 with posts 608. Thecantilever beams 606 are attached at a first end 618 of the shutter 601and the cantilever beams 607 are attached at a second end 617 of theshutter 601. The beams 606 and 607 are positioned substantially parallelto the surface 605 and are spaced from the surface 605 by a first gap619. Also the beams 606 and 607 are positioned substantially parallel tothe shutter 601 and are spaced from the shutter 601 by a second gap 620.The cantilever beams 606 and 607 may be formed thin and long so it canbend or flex without requiring significant force. Also the beams 606 and607 may be formed to have a sufficient height oriented vertically to thesurface 605 to support the weight of the shutter 601.

The shutter 601 further includes a first flange 613 that extends fromthe first end or edge 618 of the shutter 601 towards the surface 605within 5 degrees from the normal to the surface 605. The shutter 601also includes a second flange 615 that extends from the second edge 617towards the surface 605 within 5 degrees from the normal to the surface605.

The beams 606 and 607 are inclined with respect to a surface 629 of theflange 613 and form an angle 628 between 70 to 89 degrees (FIG. 6D).

The modulator 600 further includes two electrodes 614 and 616 thatextend from the surface 605 near to right angles. The electrode 614 isattached to the surface 605 with conductive pad 611 and the electrode616 is attached to the surface 605 with conductive pad 612. Theelectrode 614 and the flange 613 form a first electrostatic actuator 622and the electrode 616 and the flange 615 form a second electrostaticactuator 621.

In operation the actuator 622 applies a first force 625 to the shutter601, pulls the beams 606 that are attached at the first end 618 of theshutter 601 and moves the shutter 601 substantially in a lateraldirection 626 with respect to the first force 625 to a first position(FIG. 6E), and the actuator 621 applies a second force 627 to theshutter 601, pulls the beams 607 that are attached at the second end 617of the shutter 601 and moves the shutter 601 substantially in a lateraldirection 628 with respect to the second force 627 to a second position(FIG. 6F). The shutter 601 moves in the lateral direction 626 at least 5times more than in the direction of the first force 625.

Stored mechanical forces in the beams 606 and 607 return the shutter 601from the first or the second positions to a mechanical rest or neutralposition as shown in the FIG. 6D. The shutter 601 moves between thefirst and the second positions in a plane that is substantially parallelto the surface 605.

When shutter 601 moves from the mechanical rest position (FIG. 6D) tothe first position (FIG. 6E) the linear distance increases between theposts 608 and 609 that are attached to the ends of the beams 607. Forthis reason, the beams 607 are formed slightly curved to compensate forthe linear distance increase between the posts 608 and 609.

FIGS. 7A to 7D illustrate a light modulator 700 according to anillustrative embodiment of the invention. The modulator 700 includes alight shutter 701 constructed from a conductive material and includeslight transmitting regions 702 and light blocking regions 703. Theshutter 701 further includes a first flange 708 that is attached to theshutter 701 at a first end 706. The shutter 701 is supported on asurface 704 of a substrate 705 with four cantilever beams 712 and 714(FIG. 7C).

A first end of each cantilever beams 712 and 714 is attached to thesurface 704 with posts 716 and conductive pads 717, and a second end isattached to the shutter 701 with posts 715. The cantilever beams 714 areattached at the first end 706 of the shutter 701 and the cantileverbeams 712 are attached at a second end 707 of the shutter 701. Thecantilever beams 712 and 714 are substantially straight. The cantileverbeams 714 are inclined with respect to the flange 708 and form an angle730 between 70 to 89 degrees and the cantilever beams 712 form an angle731 near to 90 degrees with the flange 708.

The modulator 700 further includes an electrode 709 that extendsvertically from the surface 704 and is attached to the surface 704 withconductive pad 710. The electrode 709 and the flange 708 of the shutter701 form an electrostatic actuator 711.

In operation the actuator 711 pulls the beams 714 that are attached atthe first end 706 of the shutter 701 in a direction 720 and moves theshutter 701 substantially in a lateral direction 721 with respect to thedirection 720 to a first position (FIG. 7D). Stored mechanical forces inthe beams 712 and 714 return the shutter 701 from the first position toa mechanical rest or neutral position (FIG. 7A). The shutter 701 movesbetween the positions in a plane that is substantially parallel to thesurface 704.

The modulator 700 may further include a second electrostatic actuator725 formed by a second flange 722 attached to the shutter 701 at thesecond end 707 and a second electrode 723 that extends vertically fromthe surface 704 and is attached to the surface 704 with a conductive pad724. In the modulator 700 the supports 712 limit the shutter 701 and thesecond flange 722 to move closer to the second electrode 723 thereforethe second electrode 723 may be positioned at close distance from thesecond flange 722 to form an efficient actuator.

In a display a pixel addressing voltage may be applied to the secondactuator 725 for selectively holding the shutter 701 at the mechanicalneutral position.

FIGS. 8A to 8F illustrate manufacturing steps of a shutter support 800according to an illustrative embodiment of the invention similar to thesupports in modulators 600 and 700. FIG. 8A illustrates the shuttersupport 800 that includes a cantilever beam 803. A first end of the beam803 is attached to a first post 804 that connects the beam 803 to asurface 801 of a substrate 802 with a pad 805 and a second end of thebeam 803 is attached to a second post 806 which later connects to ashutter. The first post 804 and the second post 806 each have threesides and a top.

The support 800 is formed on a mold 807. The first manufacturing step isforming the mold 807 from a sacrificial material on the surface 801 ofthe substrate 802 (FIG. 8B). The mold 807 is formed with a shape of arectangular prism and has four sidewalls 808, 809, 810 and 811 and a top812. The sidewalls are oriented vertically to the surface 801 within+/−5 degrees with respect to the normal. Next steps are depositing aconformal layer of conductive material 814 on the surfaces of the mold807 and the surface 801 by a magnetron sputtering and applying aconformal layer of positive photoresist 815 on the conductive layer 814by an electrophoretic deposition or spraying (FIG. 8C).

The next step is positioning a first photomask 816 over the mold 807(FIG. 8D) and illuminating the photoresist layer 815 with a UV lightsource having collimated and inclined rays with less than 2 degreedivergence and an inclination angle 817 with respect to the surface 801between 45 to 75 degrees from directions of sidewalls 808 and 809 (FIGS.8E and 8F). The mold 807 and the first photomask 816 block the UV lightfrom the regions on the photoresist layer 815 that define the geometricshapes of the cantilever beam 803, the first post 804, the second post806 and the pad 805. A further step is positioning a second photomask818 over the mold 807 (FIG. 8G) and illuminating the photoresist layer815 from the direction of sidewall 811 (FIG. 8J). This will illuminatethe photoresist layer 815 applied on the lower part of the sidewall 811.The steps shown in FIGS. 8G and 8J may be omitted if the second post 806is formed with only two sides formed on the sidewalls 808 and 809 of themold 807 and a top.

After illuminating from all three directions the photoresist layer 815is developed and unprotected regions of the conductive layer 814 areremoved by etching. The cantilever beam 803 formed on the mold 807 has awidth equal to the thickness of the conductive layer 814.

In the case that the conductive layer 814 is formed from a material suchas aluminum that can reflect UV light, a light absorbing layer may beapplied or formed on the conductive layer 814 before applying thephotoresist layer 815. This will reduce reflections of UV light fromhorizontal and vertical surfaces. To reduce reflections from the surfaceof the photoresist layer 815, the mold and the mask may be immersed in aliquid with a similar refractive index as the photoresist layer 815.

FIGS. 9A to 9F illustrate manufacturing steps of a shutter 900 and anelectrode 905 according to an illustrative embodiment of the inventionsimilar to the modulators 600 and 700.

FIG. 9A illustrates a shutter 900 that includes a light transmittingregion 901 and a flange 902. The shutter 900 is connected to the post806 of the support 800 that was described above. FIG. 9A furtherillustrates an electrode 905 that is attached to a surface 801 of asubstrate 802 with a pad 904.

The first manufacturing step is forming a mold 910 comprising tworectangular prisms 911 and 912 from a sacrificial material on thesurface 801 of the substrate 802 (FIG. 9B). The prism 911 includes foursidewalls 914, 915, 916, 917 and a top 918. The prism 912 includes foursidewalls 920, 921, 923, 924 and a top 925. The sidewalls are orientedvertically with respect to the surface 801 within +/−5 degrees from thenormal. A via hole 926 is formed on the top 918 of prism 911 forconnecting the shutter 900 to the post 806 of support 800.

Next steps are depositing a conformal layer of conductive material 930on the surfaces of the mold 910 and the surface 801 and depositing aconformal layer of negative photoresist 931 on the conductive layer 930(FIG. 9C).

The following step is positioning a photomask 932 over the mold 910(FIG. 9D) and illuminating the photoresist layer 931 with a UV lightsource having collimated and inclined rays from directions of sidewalls916 and 924 (FIGS. 9E and 9F).

The mask 932 blocks UV light illumination of the photoresist layer 931applied on surfaces of the sidewalls 915, 916, 917, 920 and 923, and aregion of the top surface 918 where the light transmitting region 901 ofthe shutter 900 is formed. The mold blocks lower portions of surfaces ofthe sidewalls 914 and 921 where the flange 902 and the electrode 905 areformed and a portion of the surface 801 between the sidewalls 914 and921.

After illuminating from both directions the photoresist layer 931 isdeveloped and unprotected regions of the conductive layer 930 is etched.

The next step is removing the sacrificial layer and releasing theshutter 900 and the support 800.

The shutter 900 may be formed to include flanges such as the flange 902on all four edges of the shutter 900. These flanges can effectivelyblock stray light from exiting a display thereby improving contrast.

FIGS. 10A, 10B and 10C illustrate a display backlight 1000 according toan illustrative embodiment of the invention. FIG. 10A is a perspectiveview of the backlight 1000, FIG. 10B is a side view of the backlight1000 and FIG. 10C is an enlarged view of the area designated as 10C inFIG. 10B.

The backlight 1000 includes a generally planar light guide 1001constructed from acrylic or other transparent material having arefractive index n1 with a value between 1.45 and 1.6. The light guide1001 includes a top surface 1002, a bottom surface 1003, opposing sidesurfaces 1004 and 1005 and a light input end 1006. The bottom surface1003 is inclined with respect to the top surface 1002 and forms an angle1009 (FIG. 10B) with a value between approximately 0.1 degrees to 2.0degrees. The bottom surface 1003 converges with the top surface 1002 ina direction away from the light input end 1006.

The backlight 1000 further includes a light absorbing film 1010positioned proximate to the bottom surface 1003 of light guide 1001 anda plurality of light sources 1011 positioned proximate to the lightinput end 1006.

The backlight 1000 also includes a first optical layer 1015 constructedfrom a substantially transparent material having a refractive index n2with a value between approximately 1.45 and 1.6. First optical layer1015 comprises a light exit surface 1016, a light input surface 1017,and a plurality of embedded light reflectors 1018 located between lightinput surface 1017 and light exit surface 1016. The light reflectors1018 are formed from a thin light reflecting material such as aluminumor silver. The light reflectors 1018 may have a substantially flatsurface or a curved surface having a cross section with a radius ofcurvature between approximately 20 to 80 micron. The light reflectors1018 are inclined with respect to the top surface 1002 of the lightguide 1001 and form an angle 1026 with a value between approximately 20degrees and 40 degrees.

The backlight 1000 also includes a second optical layer 1020 formedbetween light input surface 1017 of the first optical layer 1015 and thetop surface 1002 of light guide 1001. The second optical layer 1020 isconstructed from a fluoropolymer or other substantially transparentmaterial having a refractive index n3 with a value between approximately1.3 and 1.4.

In operation light rays 1023 entering from the light input end 1006 oflight guide 1001 reflect from the top surface 1002 and the bottomsurface 1003 and change angles towards normal with respect to the topsurface 1002. Light rays 1023 exit the light guide 1001 when theincident angle to the top surface 1002 is less than the critical angle1024 (FIG. 10C) defined by the refractive index n1 of light guide 1001and refractive index n3 of the second optical layer 1020. Light rays1023 passing through the second optical layer 1020 enter the firstoptical layer 1015 from the light input surface 1017 and change theangle defined by the refractive index n2 of the first optical layer1015. Most light rays 1023 entering the first optical layer 1015 reflectinternally from the light exit surface 1016. Light rays exit the firstoptical layer 1015 from the light exit surface 1016 by reflecting fromembedded light reflectors 1018. Light rays reflecting from curved lightreflectors 1018 exit the first optical layer 1015 from the light exitsurface 1016 and converge at a distance 1025 from the light exit surface1016.

The backlight 1000 may also include a transparent substrate such as aglass substrate and a layer of dichroic filter interposed between thefirst optical layer 1015 and the second optical layer 1020.

Steps for fabrication of an optical layer 1108 with embedded lightreflectors or light reflecting facets 1106 are illustrated in FIGS. 11Ato 11D. In step (A) micro-prisms 1101 are constructed on the substrate1103 using photolithography from a transparent UV curing liquid polymer.In step (B) the substrate 1103 is tilted about angle 1105 (FIG. 11B) andextensions 1104 of micro-prisms 1101 are formed from the same liquidpolymer. The micro-prisms 1101 with the extensions 1104 also may bemolded. In step (C) a reflective mirror film is deposited on each facetof extensions 1104 to form light reflecting facets 1106. In step (D)grooves 1107 are filled with the same UV curing liquid polymer. FIG. 11Dillustrates a completed construction of the optical layer 1108 withembedded light reflecting facets 1106.

The optical layer 1108 may be combined with shutter assemblies 100 or401 in the modulators 300 and 400 disclosed above. The optical layer1108 may be constructed on a substrate before constructing the shutterassemblies 100 or 401 and positioned between the shutter supports. Forthe modulators 500, 600 or 700 that have a shutter located at closedistance from the surface of a substrate, embedded light reflectors maybe constructed in the substrate.

FIGS. 12A, 12B and 12C illustrate steps of manufacturing a glasssubstrate 1200 with embedded light reflectors 1205 according to anillustrative embodiment of the invention. The first step is etchinggrooves 1203 in the glass substrate 1200. The next three steps aresimilar to the steps B, C and D described above. The second step istilting the substrate 1200 and forming an extension 1204 inside eachgroove from a UV curing liquid polymer. The third step is depositing areflective mirror film on the extensions 1204 to form light reflectingfacets 1205. The fourth step is filling the grooves with the same UVcuring liquid polymer. FIG. 12C illustrates glass substrate 1200constructed with embedded light reflectors 1205. Cured polymerpreferably has substantially the same refractive index as the glasssubstrate 1200. In the backlight 1000, the first optical layer 1015 maybe replaced with the glass substrate 1200 and modulators 500, 600 or 700may be constructed on the glass substrate 1200.

FIGS. 13A and 13B illustrate a display cover assembly 1400 according toan illustrative embodiment of the invention. The cover assembly 1400includes a transparent substrate 1401 having a first surface 1402 and asecond surface 1403. The cover assembly 1400 also includes a lightdiffusing layer 1404 formed on the first surface 1402 and a lightabsorbing layer 1405 formed on the light diffusing layer 1404. For thinsubstrates with thickness 200 micrometer or less, diffusing layer 1404may be formed on the second or outer surface 1403 and the lightabsorbing layer 1405 may be formed on the inner surface 1402 of thesubstrate 1401. The light absorbing layer 1405 includes lighttransmitting regions 1407 and opaque light absorbing regions 1406. Thecover assembly 1400 may further include electrodes such as electrodes308 and 309 of modulator 300 formed on the opaque light absorbingregions 1406 of the light absorbing layer 1405 having a light reflectingmirror surfaces or a transparent conductive layer such as the electrode415 in the modulator 400.

The light absorbing layer 1405 may be formed from a conductive material.The conductive light absorbing layer 1405 may act as an EMI orelectrostatic shield in a display or an electrode for an actuator suchas the actuators in the modulator 400.

The light absorbing layer 1405 may absorb 80% or more light impingingthe opaque light absorbing regions 1406 and transmit less than 1% light.

Displays based on electromechanical light modulators may include largenumbers of modulators arranged in rows and columns. Each picture elementor pixel in a display may include one or more modulators. Forillustrative purposes the following drawings illustrate displays withonly one modulator.

FIGS. 14A and 14B illustrate a cross sectional views of a display 1500according to an illustrative embodiment of the invention. The display1500 includes a cover assembly 1501, a modulator 1502 and a backlight1503 that includes a rear reflector 1504. The cover assembly 1501includes a transparent substrate 1505, a light diffuser layer 1506formed on a first surface 1507 of the substrate 1505 and a lightabsorbing layer 1508 formed on the light diffuser layer 1506. The lightabsorbing layer 1508 includes a light transmitting regions 1509 andopaque light absorbing regions 1510. The modulator 1502 includes ashutter 1511 having light transmitting regions 1514 and light blockingregions 1515. The surface of the shutter 1511 facing the backlight 1503is a light reflecting surface and the surface facing the light absorbinglayer 1508 is a light absorbing surface. The light transmitting regions1509 of the light absorbing layer 1508 are larger than the lighttransmitting regions 1514 of the shutter 1511 and are smaller than thelight blocking regions 1515 of the shutter 1511. In FIG. 14A the shutter1511 is at a first or ON position and in FIG. 14B the shutter 1511 is ata second or OFF position. Light 1520 from the backlight 1503 impingingthe light transmitting regions 1514 of the shutter 1511 transmit throughthe light transmitting regions 1509 of the light absorbing layer 1508when the shutter 1511 is at a first position (FIG. 14A) and is absorbedin the light absorbing layer 1508 when the shutter is at a secondposition (FIG. 14B). Light impinging the light blocking regions 1515 ofthe shutter 1511 reflects back to the backlight 1503 and recycles byreflecting from the rear reflector 1504. The modulator 1502 may be anyone of the modulators disclosed above or a modulator that includes ashutter with a light reflecting surface facing the backlight 1503 forrecycling light emitted from the backlight 1503.

It is important to design a modulator wherein shutter supports do nottake substantially more display surface than required by the shutter sothe shutters may be positioned substantially close to each otherallowing only a space for the shutter movement and some conductorsbetween them.

The above disclosed shutter assemblies meet this requirement. Comparedwith some prior art shutter assemblies where shutter supports arepositioned at sides of the shutter and take more than 50% displaysurface, in the above disclosed shutter assemblies the shutter supportsare located between the shutter and a surface over which the shutter issupported and are positioned substantially within boundaries of theshutter which includes the shutter movement between first and secondpositions.

This increases light efficiency by increasing total light transmittingregions relative to the display surface and reduces the gap between rowsand columns of the display.

In the display 1500 the light absorbing layer 1508 may be formed from aconductive material and can replace the electrode 415 in the modulator400 disclosed above.

The electrodes 308 and 309 of the modulator 300 may be formed on thelight absorbing layer 1508 having light reflecting surface facing thebacklight 1503 and the shutter 101 may be supported on a surface 1522 ofthe substrate 1521. The shutter 601 of the modulator 600 and the shutter701 of the modulator 700 also may be supported on the surface 1522 ofthe substrate 1521. Spacers 508 and 509 of the modulator 500 may beformed on the light absorbing layer 1508 and the shutter 503 may besuspended from the spacers 508 and 509.

In the display 1500 the backlight 1503 emits a surface light and may bean edge lit or a direct lit backlight known from the LCD displays.

FIGS. 15A and 15B illustrate a cross sectional views of a display 1700according to an illustrative embodiment of the invention. The display1700 includes a cover assembly 1701, a modulator 1702 and a backlight1703. The cover assembly 1701 includes a transparent substrate 1705, alight diffuser layer 1706 formed on a first surface 1707 of thesubstrate 1705 and a light absorbing layer 1708 formed on the lightdiffuser layer 1706. The light absorbing layer 1708 includes a lighttransmitting regions 1709 and light absorbing regions 1710. Themodulator 1702 includes a shutter 1711 having light transmitting regions1714 and light blocking regions 1715. The surface of the shutter 1711facing the backlight 1703 may be a light reflecting surface or a lightabsorbing surface and the surface facing the light absorbing layer 1708is a light absorbing surface. The light transmitting regions 1709 of thelight absorbing layer 1708 are larger than the light transmittingregions 1714 of the shutter 1711 and are smaller than the light blockingregions 1715 of the shutter 1711. The modulator 1702 further includes asubstrate 1716 having a light exit surface 1721 and embedded lightreflecting facets 1717. The facets 1717 are curved and cause light 1720from the backlight 1703 to exit the substrate 1716 and converge at thelight transmitting regions 1714 of the shutter 1711. The shutter 1711 issupported on the surface 1721 of the substrate 1716. The backlight 1703includes a light guide 1719 an optical layer 1718 positioned between thelight guide 1719 and the substrate 1716. The backlight 1703 is similarto the backlight 1000 of FIGS. 10A to 10C. The backlight 1703 furtherincludes a light absorbing layer 1704 positioned behind the light guide1719 for absorbing stray light or light that reflects from the shutter1711.

In FIG. 15A the shutter 1711 is at a first or ON position and in FIG.15B the shutter 1711 is at a second or OFF position. Light 1720 emittedfrom the substrate 1716 transmits through the light transmitting regions1714 of the shutter 1711 and the light transmitting regions 1709 of thelight absorbing layer 1708 when the shutter 1711 is at a first position(FIG. 15A) and is blocked by the light blocking regions 1715 of theshutter 1711 when the shutter 1711 is at a second position (FIG. 15B).Light reflecting back from the light blocking regions 1715 of theshutter 1711 is absorbed in the light absorbing layer 1704.

In the display 1700 curved reflectors 1717 increase the display'sviewing angles and reduce the required moving distance of the shutter1711 between ON and OFF positions compared with flat reflectors.

The displays described above may further include spacers for maintainingprecise distance between the substrates, row and column conductorsformed on one or both substrates, one or more thin film transistors anda storage capacitor for addressing the display pixels, a ground or powerplane, a common interconnect for resetting the display pixels, dichroicor color filters and antireflection coatings.

The displays described above may be labeled as electromechanical,micromechanical, micro-electromechanical or micro-electro-mechanicalsystems (MEMS) display. The displays described above may be a monochromedisplay, a color display or a color sequential display.

Having now described the invention in detail in accordance with therequirements of the patent statutes, those skilled in this art will haveno difficulty in making changes and modifications in the individualparts or their relative assembly or fabrication methods in order to meetspecific requirements or conditions. Such changes and modification maybe made without departing from the scope and spirit of the invention, asset forth in the following claims.

The invention claimed is:
 1. An electromechanical display elementcomprising: a first and a second actuator and a shutter having a firstand a second end, said shutter supported over a surface with a pluralityof supports attached at said first and second ends, the supportsattached at said first and second ends are inclined with respect to eachother and are inclined with respect to the surface.
 2. Theelectromechanical display element of the claim 1 wherein a first forceapplied to the shutter pulls said supports attached at said first end toa near upright position with respect to the surface and moves theshutter to a first position.
 3. The electromechanical display element ofthe claim 1 wherein a first force applied to the shutter pulls saidsupports attached at said first end to a near uptight position withrespect to the surface and moves the shutter to a first position and asecond force applied to the shutter pulls said supports attached at saidsecond end to a near upright position with respect to the surface andmoves the shutter to a second position.
 4. The electromechanical displayelement of the claim 1 wherein a first force applied to the shuttermoves the shutter in a lateral direction with respect to the firstforce.
 5. The electromechanical display element of the claim 1 furtherincludes an electrode, wherein said electrode and the shutter form anelectrostatic actuator.
 6. The electromechanical display element of theclaim 1 further includes a first and a second electrode, wherein thefirst electrode and the shutter form a first electrostatic actuator andthe second electrode and the shutter form a second electrostaticactuator.
 7. The electromechanical display element of the claim 1wherein the shutter includes a first and a second electrode, each saidfirst and second electrodes forms an electrostatic actuator with a thirdelectrode.
 8. The electromechanical display element of the claim 1wherein said supports provide an electrical connection from the surfaceto the shutter.
 9. The electromechanical display element of the claim 1wherein the shutter includes a first and a second electrode, and whereinthe supports attached at said first end of the shutter provide a firstelectrical connection from the surface to the first electrode and thesupports attached at said second end of the shutter provide a secondelectrical connection from the surface to the second electrode.
 10. Theelectromechanical display element of the claim 1 wherein said supportsare located between the shutter and the surface.
 11. Theelectromechanical display element of the claim 1 wherein said supportsare substantially straight and the supports attached at said first endare substantially parallel and the supports attached at the second endare substantially parallel.
 12. The electromechanical display element ofthe claim 1 wherein said shutter includes light absorbing surfaces. 13.The electromechanical display element of the claim 1 wherein saidshutter includes a light absorbing first surface and a light reflectingsecond surface.
 14. The electromechanical display element of the claim 1wherein each said support forms an angle with the surface between 70 to85 degrees.
 15. The electromechanical display element of the claim 1wherein the shutter includes beveled edges.
 16. The electromechanicaldisplay element of the claim 1 further includes a first and a secondactuator, wherein said first and second actuators each apply a force tothe shutter substantially in the same direction and move the shutterlaterally with respect to the applied force in opposite directions. 17.An electromechanical display element comprising: a first and a secondactuator and a shutter having a first and a second end, supported over asurface with a plurality of supports attached at said first and secondends, wherein the first actuator pulls said supports attached at saidfirst end to a near position with respect to the surface and moves theshutter to a first position and the second actuator pulls the supportsattached at said second end to a near upright position with respect tothe surface and moves the shutter to a second position.
 18. Theelectromechanical display element of the claim 17 wherein each saidfirst and second actuators are an electrostatic actuator.
 19. Theelectromechanical display element of the claim 17 wherein the shutterincludes beveled edges.
 20. An electromechanical display elementcomprising: a first and a second actuator and a shutter having a firstand a second end, supported over a surface with a plurality of supportsattached at said first and second ends, wherein said first and secondactuators each apply a force to the shutter substantially in the samedirection and move the shutter laterally with respect to the appliedforce in opposite directions.